Revert "[sanitizer] Intercept sched_getaffinity."

This reverts commit r187788.

The test case is unreliable (as the test may be run in a situation in
which it has no affinity with cpu0). This can be recommitted with a more
reliable test - possibly using CPU_COUNT != 0 instead (I wasn't entirely
sure that a process was guaranteed to have at least one affinity, though
it seems reasonable, or I'd have made the change myself).

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@187841 91177308-0d34-0410-b5e6-96231b3b80d8